'Clear' (Season 3, Episode 12)
The show's third season has arguably been its most ambitious so far, splitting time between two warring human settlements and introducing about a dozen new characters. But the season's standout episode gets back to the show's roots. Rick, Carl, and the sword-toting zombie-slayer Michonne return to Rick's hometown, looking for weapons. There, they find Morgan (Lennie James) — the neighbor who helped Rick way back in the pilot. "Clear" quietly marks how much has changed since the story began, showing how the formerly level-headed Morgan has gone mad from watching his undead wife eat their son. And the chilling bookend scenes show how our hero has changed too, as he first refuses to pick up a hitchhiker, and later calmly retrieves that hitchhiker's gear when he comes across the man's dismembered body.